1. Field of the Invention
This invention relates to the formation of a microporous silicon film. More particularly, it concerns the controlled anodization and oxidation of silicon to create a porous film. By isolating and mounting the film on a porous substrate, it is possible to effect separation processes in a molecular regime.
2. Brief Description of the Prior Art
Silicon is an abundant element, relatively inexpensive, and commonly used in semiconductors. Refinements in silicon technology have had applications in the computer and integrated circuit industries.
Silicon tends to exist in crystalline form at room temperature. It is well known in the art that a silicon surface may be etched, oxidized, anodized, and bombarded with ions. Advances in silicon processing have concentrated on improved control of surface modification steps, because silicon's good physical properties allow custom-tailoring of its surface contours. For example, the formation of pores has been of particular interest. Pore sizes have decreased substantially over time. With these decreases, the potential uses for silicon have increased.
A variety of silicon methods for making pores are known in the prior art. One process for forming apertures in silicon (Abbas et al.; U.S. Pat. No. 3,962,052) requires the use of photolithographic machinery and materials on both sides of the silicon. The holes produced by this process, however, are no smaller than one micron, a size far above molecular.
A bombardment method disclosed in Price (U.S. Pat. No. 3,303,085) requires a vacuum chamber and a particle beam. There would be great utility and benefit in eliminating the need for such enormous support facilities.